1. Field of the Invention
The present invention relates to a controller circuit suitable to management of an actuator designed to position a head in a recording medium drive such as a hard disk drive (HDD) and the like.
2. Description of the Prior Art
A hard disk drive (HDD) in general includes a swinging carriage supporting a magnetic head assembly, and a voice coil motor as an actuator connected to the swinging carriage. The voice coil motor is designed to drive the swinging carriage for swinging movement in response to supply of an instructions signal specifying the controlled quantity of the swinging carriage. When the natural frequency of the swinging carriage matches with the frequency of the instructions signal, the HDD suffers from a continuous vibration of the swinging carriage. This phenomenon is in general called resonance. As disclosed in Japanese Patent Application Laid-open No. 5-159492, for example, a notch filter can be added to a controller circuit to attenuate the amplitude of a resonant frequency component in the instructions signal output from the controller circuit. The notch filter is supposed to suppress or totally prevent a continuous vibration of the swinging carriage supporting the magnetic head assembly.
In the conventional controller circuit, the cutoff frequency of a broader bandwidth should be set in the notch filter. The cutoff frequency over a broader band tends to induce a phase shift between the instructions signal supplied to the voice coil motor and the positional information signal output from the magnetic read/write head included in the magnetic head assembly. The positional information signal is output to specify the actual position of the read/write head. The aforementioned phase shift is supposed to deteriorate the response in positioning the magnetic read/write head right on a trajectory corresponding to the target recording track on a magnetic disk. It is accordingly preferable that the cutoff frequency of a narrower bandwidth can be set in the notch filter.
It is accordingly an object of the present invention to provide a controller circuit connectable to an actuator designed to position a head in a recording medium drive, capable of reliably preventing generation of resonance with the cutoff frequency of a narrower bandwidth.
According to a first aspect of the present invention, there is provided a controller circuit connectable to an actuator designed to position a head in a recording medium drive, comprising: a control signal output circuit designed to output a positioning control signal for the actuator; a filter designed to subject the positioning control signal to filtering based on a predetermined cutoff frequency; a thermal sensor detecting temperature; and a cutoff frequency determining circuit designed to determine the predetermined cutoff frequency for the filter based on the temperature.
The controller circuit is designed to generate the positioning control signal based on the positional deviation of the head from a target recording track on a recording medium. A feedback control is effected to position the head right on a trajectory corresponding to the target recording track based on the generated positioning control signal. In this case, the positioning control signal subjected to filtering serves to attenuate or reduce the amplitude of the frequency component, in the positioning control signal, corresponding to the resonant frequency to the natural frequency related to the head. A suitable cutoff frequency may be selected in the filter so as to properly reduce the amplitude of the frequency component corresponding to a measured resonant frequency in the positioning control signal.
In effecting filtering, the cutoff frequency is set in the filter based on the temperature. Accordingly, if the resonant frequency shifts in response to variation in the temperature, the cutoff frequency of the filter is allowed to follow the shift of the resonant frequency. In this case, a narrower bandwidth of the cutoff frequency still reliably achieves the reduction in the amplitude of the frequency component corresponding to the resonant frequency. The resonance or continuous vibration can reliably be prevented in the head. A rapid response can be accomplished in positioning the head right on a trajectory corresponding to the target recording track because of a narrower bandwidth of the cutoff frequency.
According to a second aspect of the present invention, there is provided a recording medium drive comprising: a head; a support member supporting the head; an actuator designed to drive the support member based on an electric current so as to position the head; a filter circuit designed to subject the electric current to filtering based on a predetermined cutoff frequency; a thermal sensor detecting temperature; and a cutoff frequency determining circuit designed to determine the predetermined cutoff frequency for the filter circuit based on the temperature.
Likewise, the amplitude of the frequency component corresponding to the resonant frequency in the positioning control signal can be reduced after the filtering in the recording medium drive. When the thus filtered positioning control signal is supplied to the actuator, an excessive or continuous vibration caused by resonance can be prevented in the head. Moreover, since the specific cutoff frequency is determined in the filter based on the temperature detected at the thermal sensor, a narrower bandwidth of the cutoff frequency still reliably achieves reduction in the amplitude of the frequency component corresponding to a specific resonant frequency in the positioning control signal in the aforementioned manner.
The aforementioned controller circuit can be realized with a microcomputer, a digital signal processor (DSP), or the like, for example. The microcomputer or DSP may be designed to effect a method comprising: generating a positioning control signal based on a positional deviation of a head from a target recording track; subjecting said positioning control signal to filtering based on a predetermined cutoff frequency; and setting said predetermined cutoff frequency based on a signal specifying a temperature when effecting said filtering.
Such a method can be realized with a computer program stored in a memory chip, said program comprising: computer program code causing an MPU or DSP to calculate a controlled quantity for positioning a head with respect to a recording medium based on a positional deviation of said head from a target recording track; computer program code causing said MPU or DSP to subject said controlled quantity to filtering based on a predetermined cutoff frequency; and computer program code causing said MPU or DSP to set said predetermined cutoff frequency based on a signal specifying a temperature when effecting said filtering. The computer program may be installed into the memory chip through any type of portable computer-readable storage medium, such as a diskette (FD), a compact disk (CD), and the like.